1. Field of the Invention
The present invention relates to a shut-off device for pipes according to the introductory part of claim 1.
2. Description of the Prior Art
The inventive shut-off device differs from a simple valve flap which constitutes a double lever with respect to the driving shaft and swivels on the seat on the housing side with each flap half from different sides regarded in the axial direction. This known valve flap necessitates a spherical contour of the sealing surfaces on the flap and housing sides, which must therefore be precisely fitted to each other. The tight flap seat must have a press fit between the valve flap and its seat on the housing side due to the pressure differences in the tubular housing. When the valve flap is opened or closed this necessitates a high driving torque. Due to the friction between the valve flap and the housing there is very great wear on the sealing surfaces in particular in the case of abrasive flow media. This wear initially causes a reduction of imperviousness. Therefore, the entire shut-off device must be frequently replaced.
In the inventive shut-off device, however, the sealing effect is maintained for long periods of time and in spite of frequent operation. There is also a small driving torque when the flap is opened and closed.